Semiconductor devices often include circuits formed in an active area of a semiconductor die. To fabricate the conventional semiconductor device, the die is mounted active area up on a substrate. The die is then encapsulated. Flip-chip semiconductor devices are fabricated by mounting the die with the active area down, toward the substrate. Thus, the circuits in the active area of a flip-chip device are less accessible than in a conventional device.
Irrespective of the type of semiconductor device, faults can occur in the circuits within the active area of the die. One such fault is an open circuit. Open circuits adversely impact the performance of the semiconductor device. Consequently, it is desirable to detect the existence and location of open circuits.
One conventional method for determining the location of an open circuit uses a SEM (scanning electron microscope) to image circuits in the die. While power is supplied to the die, the SEM images the die. Portions of the image may appear dark because electrons are attracted to a positive voltage provided by an open circuit. Thus the location of the open circuit can be detected using the SEM. Another conventional method for finding the sites of open circuits is to deprocess the die, layer by layer. Each layer is inspected to determine if the location of an open circuit is within the layer.
Although the conventional methods function, in order for the SEM to be effective, the probe of the SEM must be placed very near the circuits in the die. Thus, the die must at least be decapsulated. Furthermore, in flip-chip devices, even decapsulation does not expose the active area, which is mounted to the substrate. Thus, detection of open circuits using the SEM is made significantly more difficult. Similarly, although deprocessing can reveal the location of a short, deprocessing also destroys the device. Thus, it may be impossible to perform other tests on the device once deprocessing has commenced.
Accordingly, what is needed is a system and method for detecting shorts in a circuit of a semiconductor die. The present invention addresses such a need.